Recording needle protection arrangement for facsimile recorder

ABSTRACT

A clamp for securing the copy sheet to the drum is formed with cutouts to prevent interference of the clamp with releasing members for removing the sheet from the drum. The cutouts each have a slanted edge, the angle of slant being determined by the speed of rotation of the drum and the lead of the recording needle so that the recording needle cannot abut against the slanted edge when the needle drops into the respective cutout.

United States Patent Misawa et al.

[ Mar. 25, 1975 RECORDING NEEDLE PROTECTION ARRANGEMENT FOR FACSIMILE RECORDER Inventors: Toshihiko Misawa; Mitsuru Kondo,

both of Tokyo, Japan Assignee: Kabushiki Kaisha Ricoh, Tokyo,

Japan Filed: May 1, 1974 Appl. N0.: 465,794

Foreign Application Priority Data May 8, 1973 Japan 48-53919 US. Cl. 346/138, 346/139 C Int. Cl. Gold 15/28 Field of Search 346/138, 139 C, 125%28,

[5 6] References Cited UNITED STATES PATENTS 2,514,974 7/1950 Schauer 346/138 3,618,123 11/1971 Buddendeck 346/138 Primary Examiner-Joseph W. Hartary Attorney, Agent, or FirmFrank J. Jordan [57] ABSTRACT 4 Claims, 5 Drawing Figures PATENTEDMAR25I975 8.873986 sum 1 qf z Fig 3 PRIOR ART- Fig, 4

l6 IQ l f RECORDING NEEDLE PROTECTION ARRANGEMENT FOR FACSIMILE RECORDER The present invention relates to an improved facsimile recorder arranged to prevent damage of the recording needle caused by abutment thereof with an edge of a cutout provided in a clamp which secures the copy sheet to the drum.

In the prior art it has been customary to secure the copy sheet to a drum of a facsimile recorder using a pawl or clamp. As the drum rotates, a recording needle moves along the copy sheet parallel to the axis of the drum to reproduce the original document. The darkness of each point on the copy sheet produced by the recording needle is determined by an electrical signal fed to the recording needle by an electrical receiving unit. If the arrangement is such that the clamp is manually actuated each time a copy sheet is secured to or removed from the drum, no problems are encountered regarding damage to the recording needle through abutment thereof with the clamp. However, in a facsimile recorder in which the copy sheets are automatically secured to and removed from the drum as a copy is completed, the clamp is formed with cutouts to prevent interference of the clamp with releasing pawls or guides which remove the copy sheet from the drum. It has been found in practice using this type of automatic facsimile receiver that the recording needle is sometimes damaged when it drops into one of the cutouts through engagement with an edge of the cutout caused by the longitudinal feed of the recording needle.

It is therefore an important object of the present invention to provide an improved arrangement for a facsimile recorder or receiver which positively prevents damage to the recording needle through abutment thereofwith an edge ofa cutout ofa clamp as described above.

The above and other objects, features and advantages of the present invention will become clear from the following detailed description taken with the accompanying drawings, in which:

FIG. 1 is a fragmentary side sectional view of a facsimile recorder to which the present invention is directed shown in a copy sheet insertion condition;

FIG. 2 is similar to FIG. 1, but shows the facsimile recorder in a copy sheet removal condition;

FIG. 3 is a fragmentary top view of a prior art arrangement of the facsimile recorder of FIG. 1;

FIG. 4 is similar to FIG. 3, but illustrates the improvement according to the present invention; and

FIG. 5 is an enlarged diagrammatic view of part of FIG. 4 illustrating the geometry of the improvement of the present invention.

Referring now to FIG. 1, a facsimile recorder or re-' ceiver to which the present invention is directed includes a rotary drum l0 rotated by driving means (not shown) in the direction of an arrow A and being provided with at least one clamp or pinching pawl 12 to secure a recording medium in the form of a sheet 14 to the drum 10. As the drum rotates, a recording instrument here shown as a recording needle 16 is moved parallel to the axis of the drum 10 by a lead screw (not shown) driven by the driving means to reproduce the transmitted original document on the sheet 14. The recording needle 16 is energized by an electronic receiving unit (not shown) to continuously vary the density of the image formed thereby on the sheet 14. When an operating handle 18 is rotated in the direction of an arrow B, it engages with the pawl 12 to rotate the same clockwise so that a gap is formed between the pawl 12 and the circumference of the drum 10. The leading edge of the sheet 14 is inserted into the gap, and the handle .18 is rotated in a direction opposite to that of the arrow B to the position shown in FIG. 2, and the pawl 12 is rotated counterclockwise by a spring (not shown) to clamp the leading edge of the sheet 14 to the drum l0 and thereby secure the sheet 14 to the drum 10. The drum'10 is then rotated in the direction of the arrow A many times as the recording needle 16 is driven parallel to the axis of the sheet 14 so that the locus of the recording needle 16 on the drum 10 is a helix of very small lead compared to the length of the drum 10 so that many closely spaced lines are drawn on the sheet 14 to provide a copy of satisfactory resolution. A roller 20 is provided to guide the sheet 14, and a guide member or releasing pawl 22 is movable into engagement with the surface of the drum 10 to release and guide the sheeet 14 from the drum 10 after a recording operation is completed. A releasing arm 24 is normally biased in the direction of an arrow C by a tension spring 26 out of engagement with the pawl 12, but is manually or automatically movable in the direction of an arrow D before the leading edge of the sheet 14 reaches the pawl 22 to rotate the pawl 12 clockwise to release the leading edge of the sheet 14. Thereafter, the sheet 14 will be removed from the drum 10 and be ejected from the recorder in the direction of an arrow E.

FIG. 3 shows a prior art arrangement of the pawls l2 and 22. In FIG. 3, three separate pawls l2 and two pawls 22 may be provided, but the same results can be obtained using a unitary pawl 12 if it is suitably shaped. For the purpose of simplicity of description, the latter case will be assumed, and a single pawl 12 is formed with cutouts 30 which are aligned with and appreciably wider than the pawls 22 so interference of the pawls 12 with the pawls 22 during rotation of the drum 10 is prevented. An arrow F represents the direction of movement of the recording needle 16.

As mentioned above, no problems are encountered when the recording needle 16 engages with the pawl 12 or even drops into one of the cutouts 30 under most conditions due to the design of the component parts. However, if the recording needle 16 should drop into a cutout 30 very close to its upper right corner as viewed in FIG. 3, if the relative movement of recording needle 16 in the direction of the arrow F is sufficiently greater than the rotation of the drum 10 in the direction of the arrow A, the recording needle 16 might abut against the right side of the cutout 30 and be damaged, bent or broken.

The present invention effectively prevents the occurance of this condition as shown in FIG. 4. Modified cutouts 32 replace the cutouts 30, and each comprise a rectangular portion 320 which is essentially equivalent to the cutout 30 and a triangular portion 32b having a slanted edge 32c. The angle between the direction of movement of the recording needle 16 and the slanted edge 320 is selected on the basis of the speed of rotation of the drum 10 and the lead of the recording needle 16 per revolution of the drum 10, so that said angle is less than the helix angle of the locus of the recording needle 16 on the drum 10.

As is clear to those skilled in the art, even if the recording needle 16 drops into the cutout 32 just at. the upper right corner of the cutout 32 as viewed in FIG. 4, the locus of the recording needle 16 on the drum 10 will always be leftward of the slanted edge 32c as shown because the locus of the point of intersection of a line passing through the recording needle 16 and oriented in the direction F with the slanted edge 32c will move rightward as shown faster than the recording needle 16. By this arrangement, it is impossible for the recording needle 16, to abut with the slanted edge 32c, even if the recording needle 16 drops into the cutout 32 from a point on the slanted edge 320. By this novel conception, the arrangement of the present invention effectively prevents damage to the recording needle 16 caused by abutment thereof with an edge of the cutout of the pawl 12.

FIG. shows the geometry of a cutout 32 in greater detail. It will be assumed that the pawl 12 is curved to be coaxially conjugate to the circumference of the drum 10. The depth d of the cutout 32 will then correspond to the arc length of the cutout 32 in the direction of rotation of the drum l0 represented in a plane. A character 1 represents the displacement in the direction ofthe arrow F of the recording needle 16 during the interval in which the drum has rotated through an angle producing displacement equal to the depth d of the circumference of the drum 10. The case shown is a limiting case in which the angle 6 between the direction of movement of the recording needle 16 and the slanted edge 32c is equal to the arctangent of the displacement 1 divided by the depth d of the cutout 32. The angle 0 in this limiting case is equivilant to the helix angle of the locus of the recording needle 16 on the drum.

However, to positively ensure that the recording needle 16 will not abut with the slanted edge 32c, the angle 0 must be smaller than the helix angle, or expressed mathematically 0 arctan By the above simple computation, the maximum value of the angle 0 can be easily computed, and damage to the recording needle 16 caused by abutment thereof with the slanted edge 32c can be positively prevented.

What is claimed is:

I. In a recording device having a rotary drum carrying a recording medium and a recording instrument movable along the circumference of the recording medium substantially parallel to the axis of the drum, the recording medium being secured to the drum by a clamp formed with a cutout to prevent interference of the clamp with a member for removing the recording medium from the drum, an improvement to prevent the recording instrument from being damaged by engaging with a side of the cutout of the clamp, the improvement being that the cutout has a slanted edge determined by the rotational speed of the drum and the speed of movement of the recording instrument.

2. The improvement of claim 1, in which the width of the cutout increases in the direction of movement of the recording instrument.

3. The improvement of claim 1, in which the width of the cutout is appreciably greater than the width of the member for removing the recording medium from the drum.

4. The improvement of claim 1, in which the cutout has a rectangular portion and a triangular portion cornprising the slanted edge respectively arranged in the direction of movement of the recording instrument, the angle between the direction of movement of the recording instrument and the slanted edge of the triangular portion of the cutout being less than the arctangent of the depth of the cutout divided by the displacement of the recording instrument during an interval in which the drum has rotated through an angle producing displacement of the circumference of the drum substantially equal to the depth of the cutout.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,373,986 DATED March 25, 1975 INVENTOWS) Toshihiko MISAWA; Mitsuru KONDO it as certified that error appears In the above-identified patent and that said Letters Patent are harrz xy corrected as shown below- Delete Figures 6 to 8.

Signed and Scaled this twenty-second Day of July 1975 [SEAL] A nest" RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Parents and Trademarkx UNiTED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,873,986 DATED March 25, 1975 TNVEMORtS) Toshihiko MISAWA; Mitsuru KONDO it is certified hat error appears m the above-identified patent and that said Letters Patent are tram; corrected as shown below Delete Figures 6 to 8.

Signed and Scaled this twenty-second Day Of July 1975 [SEAL] Arrest.-

RUTH C. MASON Arresting Officer 

1. In a recording device having a rotary drum carrying a recording medium and a recording instrument movable along the circumference of the recording medium substantially parallel to the axis of the drum, the recording medium being secured to the drum by a clamp formed with a cutout to prevent interference of the clamp with a member for removing the recording medium from the drum, an improvement to prevent the recording instrument from being damaged by engaging with a side of the cutout of the clamp, the improvement being that the cutout has a slanted edge determined by the rotational speed of the drum and the speed of movement of the recording instrument.
 2. The improvement of claim 1, in which the width of the cutout increases in the direction of movement of the recording instrument.
 3. The improvement of claim 1, in which the width of the cutout is appreciably greater than the width of the member for removing the recording medium from the drum.
 4. The improvement of claim 1, in which the cutout has a rectangular portion and a triangular portion comprising the slanted edge respectively arranged in the direction of movement of the recording instrument, the angle between the direction of movement of the recording instrument and the slanted edge of the triangular portion of the cutout being less than the arctangent of the depth of the cutout divided by the displacement of the recording instrument during an interval in which the drum has rotated through an angle producing displacement of the circumference of the drum substantially equal to the depth of the cutout. 